Ignition distributor



Nov. 29, 1966 R. K. FRANK ETAL 3,289,020

IGNITION DISTRIBUTOR Filed Dec. 9, 1963 2 Sheets-Sheet 1 INVENTORY ,C 3 ROBERT K. FRANK I 41 PAM-'0 SCH/VE/DER BY W/Z 1 MM E s/w/v/v ATTORNEY 1966 R. K. FRANK ETAL IGNITION DISTRIBUTOR 2 Sheets-Sheet Filed Dec.

x w NM 45 x QM r a? 5R1 0 0% RAW INVIFNTORJ' ATTORNEY United States Patent 3,289,020 IGNITION ISTRIBUTOR Robert K. Frank, Mount Clemens, Alfred Schneider,

Detroit, and William F. Shunn, Fraser, Mich., assignors to Holley Carburetor Company, Warren, Mich., a corporation of Michigan Filed Dec. 9, 1963, Ser. No. 328,795 Claims. (Cl. 31070) This invention relates generally to ignition systems for internal combustion engines, and more particularly to ignition distributors for ignition systems wherein switching of current flow to the primary winding of the ignition coil is controlled by a semiconductor such as a transistor.

The usual ignition system for an internal combustion engine includes an ignition coil and an engine driven ignition distributor, the latter having a set of breaker contacts operated by an engine driven cam so that the opening and closing of the contacts controls the flow of current to the primary winding of the ignition coil. One problem with this type of ignition system is that wear of moving parts and arcing at the breaker contacts results in their deterioration so that they must be periodical 1y replaced.

More recently, ignition systems have been proposed wherein switching of the primary coil current is accomplished by a semiconductor device such as a transistor, rather than by a set of breaker contacts. However, in such systems the transistor has to be pulsed or triggered so that its switching function is accomplished in proper timed relation with the operation of the engine. This triggering has been accomplished in One of two ways. In some systems, the prior cam-operated breaker contacts are retained, but they function only to pulse or trigger the transistor so that deterioration thereof by arcing is greatly reduced; in other systems, the cam-operated breaker contacts are replaced by a so-called pulse generator comprising a pulse wheel and a magnetic pick-up device, the advantage of this triggering means being that the only moving part is the rotating pulse wheel that cannot are or wear.

Regardless of the type of transistorized system employed, a necessary portion of the system is the engine driven distributor unit having means to trigger the transistor in proper timed relation with the engine and to distribute the high voltage to the individual spark plugs. However, in every instance known to date, installation of a magnetically-pulsed transistor-controlled ignition system requires a distributor unit specially designed for the system. In other words, whether the above proposed transistorized ignition systems are intended as original equipment or as a replacement for the breaker contact type systems furnished as original equipment on existing engines, it has been considered necessary to replace the original distributor with another specially designed distributor, obviously an expensive proposition.

The price of these transistorized ignition systems is relatively high; thus, anything that can be done to reduce the cost thereof will greatly contribute to their acceptance by the public.

Accordingly, a general object of this invention is to inexpensively provide a distributor unit for a magneticallypulsed, semiconductor-controlled ignition system.

Another object of the invention is to provide a method and apparatus for converting the usual breaker contactcontrolled ignition system found on most existing engines to a magnetically-pulsed, transistor-controlled system, but without having to replace the entire distributor unit. That is, the invention enables the conversion of an existing breaker contact type distributor unit, regardless of its specific structure, to a pulse generator type distributor by replacing the breaker contacts with a magnetic pick-up ice unit, the latter being mounted in generally the same manner as the replaced breaker contacts. The conversion is completed by removing the condenser, if one is not required, and by connecting a suitable transistorized pulse amplifier and primary coil current switching unit into the system. Contrary to prior belief, it has now been discovered that if certain novel features are provided in the pulse amplifier and switching unit, then the original distributor cam will serve as the pulse wheel, without any modification thereof being required.

Still another object of the invention is to provide a method and apparatus suitable for converting a breaker contact-trigger type transistor-controlled ignition system to a magnetically-triggered type transistor-controlled system.

A more specific object of the invention is to provide an efficient standard design magnetic pick-up which unit can be properly mounted on any existing breaker contact type ignition distributor for the purpose of converting the same to a pulse generator type distributor wherein the distributor cam, or a modification thereof, is employed as the pulse wheel.

Another object of the invention is to provide a magnetic pick-up device that is directly interchangeable with the conventional breaker contacts and adapted to be pulsed by the lobes of the original distributor cam, or some modification thereof, such that adequate voltage and/or current signals, suitable for triggering a semiconductor type primary coil current switching unit, will be generated upon rotation of the cam.

A still further object of the invention is to provide a magnetic pick-up unit that is rugged in construction but small enough to be mounted in the limited space available in prior art distributors, inexpensive to manufacture and easy to install, and capable of producing pulse signals of proper amplitude and shape when the original distributor cam is employed as a pulse wheel.

Other objects and advantages of the invention will become more apparent upon reference to the following specification and the accompanying drawings wherein:

FIGURE 1 is a schematic illustration of a typical breaker contact-controlled ignition system;

FIGURE 2 is a plan view of a typical distributor unit for the system shown in FIGURE 1, with the distributor cap removed;

FIGURE 3 is a schematic illustration of a magnetically-pulsed, transistor-controlled ignition system;

FIGURE 4 is a plan view of the distributor shown by FIGURE 2, converted according to the invention for use in the ignition system shown by FIGURE 3;

FIGURE 5 is a perspective view illustrating in greater detail the adaptor plate shown by FIGURE 4;

FIGURE 6 is an enlarged plan view of the magnetic pick-up unit shown by FIGURE 4;

FIGURE 7 is a view similar to FIGURE 6, with portions thereof in cross section to better illustrate the details of construction;

FIGURE 8 is an actual size perspective view of the magnetic pick-up unit shown by FIGURES 4, 6 and 7; and,

FIGURE 9 is a schematic illustration of the magnetic circuit in the pick-up unit shown by FIGURES 4 and 6-8.

Referring now to the drawings in greater detail, FIG- URE 1 illustrates schematically a typical prior art breaker contact-controlled ignition system 10, including the usual battery 12, ignition switch 14, ignition coil 16 including a primary winding 18 and a secondary winding 20, a spark plug 22 for each engine cylinder, engine driven cam 23, breaker contacts 24, condenser 26 and rotor and distributor terminals 28.

FIGURE 2 illustrates a typical distributor unit 30 for an ignition system such as that shown by FIGURE 1, the distributor unit having the rotor and distributor cap (distributor 28) removed therefrom so as to expose the usual movable breaker plate 32 on which the breaker contacts 24 and condenser 26 are mounted.

The above described ignition system is very well known to those versed in this art, and the particular ignition distributor shown by FIGURE 2 is the same as that disclosed in Larges 3,062,929. This prior art system is shown primarily to aid in illustrating how the invention may be practiced, and no additional discussion need be given except to point out that the cam 23 for operating the breaker points is usually either formed integrally with or press-fit on a shaft 25 extending through the distributor and driven by the engine, as shown by Larges.

Many distributor units, regardless of their specific design, have means for advancing or retarding the spark, either by rotating the breaker plate on which the breaker contacts are mounted with respect to the cam and/or by rotating the cam with respect to the distributor shaft. In FIGURE 2, the breaker contact bracket 34 is secured to the breaker plate 32, and the breaker plate is pivotably mounted for rotation about the axis of the cam 23, as shown by Larges. As is typical of many prior art distributors, the breaker plate 32 is formed with a pair of threaded holes and the breaker contact bracket 34 is formed with a pair of elongated openings 36 and 38 that may be aligned with the threaded holes in the breaker plate so that screws 40 and 42 may be employed to adjustably secure the bracket 34 on the plate 32.

FIGURE 3 illustrates schematically a magneticallypulsed semiconductor-controlled ignition system 44 including a battery 46, an ignition switch 48, a pulse generating device 50 including the cam 23 serving as a pulse wheel and a so-called magnetic pick-up unit 54, a semiconductor-controlled pulse amplifier and switching unit 56, an ignition coil 58 having a primary winding 60 and a secondary winding 62, rotor and distributor terminal element 66 and a spark plug 68 for each engine cylinder. It will be apparent that the pulse generator 50 and rotor and distributor terminal element 66 are preferably mounted in a distributor unit generally similar to that shown by Larges, so that both the cam pulse wheel 23 and the rotor 67 may be driven by the distributor shaft 25.

It should be stated that the details of the pulse amplifier and switching unit 56, and its connection in the system 44 shown by FIGURE 3, form no part of this invention and may be of any suitable design, such as that shown by Johnson 2,852,589 for example. This invention is limited generally to method and apparatus for conveniently and inexpensively retrofitting a distributor unit such as that shown in FIGURE 2 to one such as that shown by FIGURE 4, whether or not the original cam 23 is employed as the pulse wheel, and more specifically to a magnetic pick-up unit that may be employed in making the retrofit.

FIGURE 4 illustrates a distributor unit 70 identical to that shown in FIGURE 2, except as modified in accord ance with the invention for use in the ignition system shown by FIGURE 3. Accordingly, all common elements bear identical reference numerals. It will be noted generally that the breaker contact bracket 34 and condenser 26 of FIGURE 2 have been removed, the bracket 34 having been replaced by a magnetic pick-up unit 54 (see FIGURE 6) secured to an adaptor plate 74 (see FIG- URE which, in turn, is secured to the breaker plate 32.

Referring now to FIGURE 5, it will be seen that the adaptor plate 74 is formed to provide a recessed portion 78 so as to not interfere with the shaft 25 and cam 23 when it is secured to the breaker plate 32. For purposes of retrofitting the particular distributor shown by FIG- URE 2, the adaptor plate 74 has openings 80 and 82 formed therein so that it may be secured to the breaker plate 32 by means of screws 84 and 86, respectively,

screw 84 engaging the same threaded opening in breaker plate 32 as that engaged by screw 40 in FIGURE 2 and screw 86 engaging the same threaded opening in breaker plate 32 as screw 90 employed to secure the condenser in FIGURE 2. It will thus be apparent that a generally similar adaptor plate may be provided for any prior art distributor having a breaker plate; as a practical matter, it has been found that a set of such adaptor plates, each of a slightly different design, will cover the field. The plate 74 is also formed with a pair of threaded openings 92 and 94, the center-line distance of which is preferably identical to but the exact location of which may be different for the set of adaptor plates referred to above.

As is known in the art, magnetic pick-up devices generate voltage and/ or current signals due to the fact that a coil is placed in the magnetic field of a magnet. When a soft iron or other wheel having discrete lobes thereon is rotated in the vicinity of the magnetic field, the field is disturbed, causing lines of magnetic flux to link or cut across the turns of the coil, each such disturbance resulting in a voltage and/ or current pulse in the coil. These signals or pulses can then be amplified and employed to trigger the semiconductor current switching device.

To obtain maximum flux linkages, and thus maximum pulses, the coil of the magnetic pick-up is ideally centered in the magnetic field, directly between the permanent magnet and the pulse wheel. However, space limitations in prior art ignition distributor units prohibit this ideal construction. Accordingly, it is necessary, in order to retrofit prior art distributors, to provide a particular magnetic field pattern by the use of a specially shaped and oriented magnet and to then provide a pole piece tending to reshape the flux pattern of this special magnet. The object of this special construction is to concentrate as much of the magnetic flux as possible in the limited space available for the pick-up coil, the purpose of the pole piece being to reduce flux leakage to a minimum while redistributing the magnetic field sufliciently to provide adequate linkage of the turns of the necessarily mislocated coil.

With the above discussion in mind and referring now to FIGURES 4 and 6-8, it will be seen that the magnetic pick-up unit 54 is assembled on a bracket 96, which is very similar to bracket 34 on which the breaker contacts 24 are assembled. The bracket 96 is formed with a pair of elongated openings or slots 98 and 100, the center-tocenter distance of which is the same as the center-tocenter distance between threaded openings 92 and 94 formed in the adaptor plate 74, and a pair of up-turned flanges or projections 102 and 104. It will be apparent, however, that the slots 98 and could be spaced to receive the screws 40 and 42 of FIGURE 2, in which case the unit 54 could be mounted directly on the breaker plate 32 without the use of the adaptor plate 74.

A permanent magnet 106 and a core member 108 are secured to the flange 102 in any suitable manner such as riveting, the core member 108 being formed to provide a portion 110 extending across the bracket 96. A suitably wound coil 112 is positioned over the inwardly extending portion 110 so that it becomes a core for the coil, one end of the coil being connected to the bracket 96 as a ground and the other end of the coil being connected to an insulated post on the other flange 104, the post having a lead 114 extending therefrom adapted to be connected to the pulse amplifier and switching unit 56.

Looking further at FIGURE 7, it will be seen that the coil 112 is wound on a spool 116, which may be formed from some inexpensive non-metallic material, having a rectangular tubular portion 118 fitting over the portion 110 of the core member 108 and connecting the end portions 120 and 122, portion 122 having a laterally extending tab 124 formed with an opening to receive the rivet 126 by which the connector of the lead 114, the connector on one end 128 of the coil 112, the insulating sleeve 130 and the tab 124 are secured to the flange 104 of the bracket 96. The sleeve insulates the flange 104 from the lead 114 and the coil 112. Rivets 132 secure the core member 108, the magnet 106 and the connector for the other end 134 of the coil 112 to the flange 102.

As stated previously, it would be preferable to place the coil 112 between the magnet 106 and the cam 23. However, the space available within most prior art distributors is not sufiicient to permit such a construction. Furthermore, since the invention involves retrofitting prior art distributors to provide a pulse generator for a semiconductor type ignition system it is less expensive and much better practice from a sales standpoint to provide a standard magnetic pick-up design which can be mounted in a variety of prior art distributors through the use of a set of adaptor plates.

It will be noted that the magnet 106 is positioned so that its length extends along a chord of the distributor housing, rather than radially; also, the magnet is oriented so that its poles are across its width, rather than at the ends thereof. Securing the pole piece 103 along one side of the magnet provide a low reluctance path for the lines of flux, and mounting the coil on the end 110 of the pole piece places it in a region of sufficient flux density. That is, the pole piece 108 redistributes a significant amount of the field of the magnet 106 to a position between the flange 102 and the pole piece 108.

The above construction also permits attachment of the end 134 of the coil directly to the solid and closely adjacent flange 102 and the other end 124 of the coil to the other solid and closely adjacent flange 104, rather than to loose leads. In other words, the wire from which the coil is formed is necessarily very fine and location of the coil between the flanges 102 and 104 provides needed protection for these connections.

As previously mentioned, magnetic pick-up units are employed in a number of devices, and they may be purchased as standard items. Usually these magnetic pickup units comprise a cylindrical magnet positioned in a soft iron, closed-end hollow cylinder with the south pole, for example, engaging the bottom of the cylinder. A rod or other similar soft iron member engages the north pole of the magnet and extends axially through the cylinder, beyond the top edge thereof. The coil is wound around the rod member, and the lines of flux flow radially from the rod member to the inner wall of the cylinder. When a soft iron element passes by such a magnetic pick-up, the lines of flux pass from the rod-like member, through the soft iron element and thence down the walls of the cylinder and back to the south pole of the magnet. This variation in the flux lines passing through the coil causes the pulse signal.

However, as already stated, a commercially available magnetic pick-up such as that described above cannot be employed to retrofit a breaker contact type ignition distributor because there is not suflicient space within the distributor housing for the size pick-up required to provide an adequate signal. It will be noted from the above discussion that the magnetic pick-up disclosed herein employs a magnet oriented so that the large area opposite sides thereof constitute the poles, thus providing relatively large pole faces. The magnet is positioned on the bracket in a manner so that when the pick-up unit is installed in the distributor housing the magnet is positioned near the wall of the annular housing where there is room for it. The pole piece is relatively large so as to provide a low reluctance path capable of transferring a high flux density to a position within the coil. Thus, until a lobe of the cam is positioned closely adjacent the free end of the pole piece, which forms an acute angle with the magnet, a heavy concentration of flux passes through the windings on one side of the coil and back to the south pole of the magnet; when a lobe of the cam moves to the position directly opposite the free end of the pole piece, the flux lines pass not through the coil but into the cam and thence back to the south pole of the magnet. FIGURE 8,

6 which disregards flux leakage and is thus ove'r simplified, illustrates the above described change in the flux path that results in pulses in the coil.

From the above description, it will also be apparent that a magnetic pick-up unit 54 may be secured, with or without the use of adaptor plates, in any prior art distributor housing in a manner so that it and the distributor cam provide a pulse generator capable, when the lobes of the cam disturb the magnetic field concentrated by the core member in the area of the coil, of causing voltage and/or current pulses in the coil. These pulses can then be amplified, if necessary, and employed to trigger a semiconductor device which, in turn, switches the current in the primary winding of the ignition coil of the system shown by FIGURE 3.

The use of adaptor plates enables a standard design magnetic pick-up unit to be assembled in any prior art dis-tributor. A magnetic pick-up unit embodying the invention is constructed and arranged so that it is inexpensive and easy to manufacture and install, and it is small enough so that it will fit into any distributor with room for adjustment thereof with respect to the cam. The connections of the ends of the coil are protected so that the unit need be handled with only reasonable care.

In the magnetic pick-up device shown, one end of the coil is connected to the bracket to provide a ground while the other end of the coil is insulated from the bracket, as would be required for negative ground ignition systems. For positive ground systems, both ends of the coil would be insulated from the bracket and connected to separate lead wires such as the lead wire 114.

While but one embodiment of the invention has been shown and described, it is apparent that modifications thereof may be made, and no limitations are intended except as recited in the following claims.

What we claim as our invention is:

1. A magnetic pick-up unit adapted to be secured within the housing of an ignition distributor having a cam so as to provide a pulse generator, said unit comprising a bracket having means for securing the same within said housing, a permanent magnet secured to said bracket, said magnet having parallel oppositely-disposed pole faces, the combined surface area of said pole faces exceeding the other surface area of said magnet, said magnet being positioned along the outer edge of said bracket, a pole piece secured to one pole of said magnet, said pole piece having a free end portion extending across said bracket and toward the axis of said cam, said free end portion of said pole piece and a pole surface of said magnet forming an acute angle, and a coil mounted on said free end portion, the arrangement of the above recited elements of said magnetic pick-up being such that magnetic flux normally passes from one pole face of said magnet through said pole piece and thence across said coil and back to the other pole face of said magnet.

2. A magnetic pick-up unit comprising a bracket having a base portion and spaced flanges extending from said base portion, one of said flanges having secured thereto a permanent magnet and a pole piece, said pole piece having the free end portion thereof formed to extend parallel to and across said base portion at a point between said flanges, a spool positioned on said inwardly bent portion of said pole piece, said spool having a tab extending from one end thereof and engaging said other flange, a coil wound on said spool, one end of said coil being secured to said one flange so as to provide an electrical ground through said base portion, the other end of said coil being secured to the other of said flanges in a manner to be electrically insulated from said bracket, an electrical lead extending from said other flange and connected to said other end of said coil, said base portion of said bracket having openings at the opposite ends thereof to receive screws for mounting said bracket.

3. A magnetic pick-up unit adapted to be adjustably secured to the breaker plate of an ignition distributor having a rotatable multi-lobe cam so as to provide a pulse generator, said unit comprising a bracket having a base portion and spaced flanges extending from said base portion, one of said flanges having secured thereto a permanent magnet and a pole piece, said pole piece having the free end portion thereof formed to extend parallel to and across said base portion at a point between said flanges, a spool positioned on said inwardly bent portion of said pole piece, said spool having a tab extending from one end thereof and engaging said other flange, a coil wound on said spool, at least one end of said coil being secured to the one of said flanges in a manner to be electrically insulated from said bracket, an electrical lead extending from said other flange and connected to said other end of said coil, said base portion of said bracket having openings at the opposite ends thereof to receive screws for connecting said bracket to said breaker plate, said openings being such that said magnetic pick-up unit may be adjusted on said breaker plate in a direction par-allel to said inwardly extending portion.

4. A magnetic pick-up unit adapted to be secured within the housing of an ignition distributor having a rotatable lobed cam so as to provide a pulse generator, said unit comprising a bracket having a base portion and spaced first and second projections extending from said base portion, said first projection having secured thereto a permanent magnet and a pole piece, said pole piece having the free end portion thereof formed to extend between said projections, parallel to and across said base portion, a spool positioned on said free end portion of said pole piece, said spool having a tab extending from one end thereof and engaging said other flange, a coil wound on said spool, one end of said coil being secured to said first projection so as to provide an electrical ground through said base portion, the other end of said coil being secured to said second projection in a manner to be electrically insulated from said bracket, an electrical lead extending from said second projection and connected to said other end of said coil, said base portion of said bracket having elongated openings at the opposite ends thereof to receive screws for connecting said bracket to said housing, the major axes of said openings being substantially parallel to said free end of said pole piece so that said magnetic pick-up unit may be adjusted on said housing in a direction parallel thereto.

5. A magnetic pick-up unit adapted to be secured within the housing of an ignition distributor having a rotatable lobed cam so as to provide a pulse generator, said unit comprising a bracket having a base portion and spaced first and second projections extending from said base portion, said first projection having secured thereto a permanent magnet and a pole piece, said pole piece having the free end portion thereof formed to extend between said projections, parallel to and across said base portion, a spool positioned on said free end portion of said pole piece, said spool having a tab extending from one end thereof and engaging said other flange, a coil wound on said spool, at least one end of said coil being secured to one of said projections so as to be electrically insulated from said bracket, said base portion of said bracket having elongated openings at the opposite ends thereof to receive screws for connecting said bracket to said housing, the major axes of said openings being substantially parallel to said free end of said pole piece so that said magnetic pick-up unit may be adjusted on said housing in a direction parallel thereto.

6. A pulse generator comprising a rotating member having a plurality of projections formed thereon, and a magnetic pick-up unit mounted adjacent said projections, said magnetic pick-up unit including a bracket, said bracket having a pair of spaced flanges extending therefrom, one of said flanges having a permanent magnet secured thereto, a member providing a low reluctance secured to said magnet, said member having a free end portion thereof formed so as to extend between said flanges parallel to said base portion and toward the axis of said rotating member, a coil mounted on said free end portion, one end of said coil being connected to one of said flanges so as to provide an electrical ground and the other end of said coil being connected to the other of said flanges in a manner to be electrically insulated therefrom, a lead wire electrically connected to said other end of said coil, said permanent magnet being oriented in a manner so that one of its poles is at the face thereof engaging said one flange and the other pole is at the face thereof engaging said low reluctance member, said member serving to provide a path of low reluctance so as to concentrate the magnetic flux in the area of said coil whereby each of said projections upon rotation thereof disturbs said fiux and causes a distinct pulse in said coil.

7. A pulse generator for a semiconductor-controlled type ignition system, said pulse generator comprising an annular housing having a drive shaft extending axially therethrough, said drive shaft having a lobed cam formed thereon, and magnetic pick-up mounted adjacent said cam, said magnetic pick-up unit including a bracket secured within said housing, said bracket having a base portion and a pair of spaced projections extending therefrom, one of said projections having a permanent magnet secured thereto, a member providing a low reluctance path secured to said magnet, said member having a free end portion thereof formed so as to extend between said projections parallel to said base portion and toward the axis of said cam, a coil mounted on said free end portion, said permanent magnet being oriented in a manner so that one of its poles is at the face thereof engaging said one projection and the other pole is at the face thereof engaging said low reluctance member, said member serving to provide a path of low reluctance so as to concentrate the magnetic flux in the area of said coil whereby a lobe of said cam upon rotation thereof disturbs said flux and causes a distinct pulse in said coil.

8. A pulse generator for a semiconductor-controlled type ignition system, said pulse generator comprising a housing having a drive shaft extending axially therethrough, said drive shaft having a pulse wheel thereon, and a magnetic pick-up unit mounted adjacent said pulse Wheel, said magnetic pick-up unit including a bracket secured within said housing, said bracket having a base portion, a magnet secured to said bracket, a member providing a low reluctance path secured to said magnet, said member having a free end portion thereof formed so as to extend across said base portion and toward the axis of said pulse wheel, a coil mounted on said free end portion, said magnet being oriented in a manner so that one of its poles is at the face thereof engaging said low reluctance member, said member serving to provide a path of low reluctance so as to concentrate the magnetic flux in the area of said coil whereby said pulse wheel upon rotation thereof disturbs said flux and causes distinct pulses in said coil,

9. A pulse generator for a semiconductor-controlled type ignition system, said pulse generator comprising a rotating member having projections formed thereon, and a magnetic pick-up unit mounted adjacent said rotating member, said magnetic pick-up unit including a bracket, said bracket having a base portion, a magnet secured to said bracket, a member providing a low reluctance path secured to said magnet, said member having a free end portion thereof formed so as to extend across said base portion and toward the axis of said rotating member, a coil mounted on said free end portion, said magnet being oriented in a manner so that one of its poles is at the face thereof engaging said low reluctance member, said member serving to provide a path of low reluctance so as to concentrate the magnetic flux in the area of said coil whereby said projections upon rotation thereof disturb said flux and cause distinct pulses in said coil.

10. A magnetic pick-up unit comprising a bracket having a base portion and spaced first and second projections extending from said base portion, said first projection having secured thereto a permanent magnet and a pole piece, said pole piece having the free end portion thereof formed to extend between said projections, parallel to and across said base portion, a spool positioned on said free end portion of said pole piece, a coil Wound on said spool, said base portion of said bracket having elongated openings at the opposite ends thereof to receive screws for mounting said bracket, the major axes of said opening being substantially parallel to said free end of said pole piece so that said magnetic pick-up unit may be adjusted in a direction parallel thereto.

References Cited by the Examiner UNITED STATES PATENTS 2,824,245 2/1958 Trevilt 310168 3,145,324 8/1964 Race 31070 3,198,974 8/1964 Dusenberry et al. 310-70 10 MILTON O. HIRSHFIELD Primary Examiner.

A. J. ROSSI, Assistant Examiner. 

1. A MAGNETIC PICK-UP UNIT ADPTED TO BE SECURED WITHIN THE HOUSING OF AN IGNITION DISTRIBUTOR HAVING A CAM SO AS TO PROVIDE A PULSE GENERATOR, SAID UNIT COMPRISING A BRACKET HAVING MEANS FOR SECURING THE SAME WITHIN SAID HOUSING, A PERMENENT MAGNET SECURED TO SAID BRACKET SAID MAGNET HAVING PARALLEL OPPOSITELY-DISPOSED POLE FACES, THE COMBINED SURFACE AREA OF SAID POLE FACES EXCEEDING THE OTHER SURFACE AREA OF SAID MAGNET, SAID MAGNET BEING POSITIONED ALONG THE OUTER EDGE OF SAID BRACKET, A POLE PIECE SECURED TO ONE POLE OF SAID MAGNET, SAID POLE PIECE HAVING A FREE END PORTION EXTENDING ACROSS SAID BRACKET AND TOWARD THE AXIS OF SAID CAM, SAID FREE END PORTION OF SAID POLE PIECE AND A POLE SURFACE OF SAID MAGNET FORMING AN ACUTE ANGLE, AND A COIL MOUNTED ON SAID FREE END PORTION, THE ARRANGEMENT OF THE ABOVE RECITED ELEMENTS OF SAID MAGNETIC PICK-UP BEING SUCH THAT MAGNETIC FLUX NORMALLY PASSES FROM ONE POLE FACE OF SAID MAGNETIC THROUGH SAID POLE PIECE AND THENCE ACROSS SAID COIL AND BACK TO THE OTHER POLE FACE OF SAID MAGNET. 